The Microsoft attack seems to have had a smaller impact than the others.

“During our investigation, we found a small number of computers, including some in our Mac business unit, that were infected by malicious software using techniques similar to those documented by other organizations,” Microsoft wrote.

The website infected the programmers’ computers, via their web browser’s Java plugin. Initially the malware appears to have targeted Macs, but Reuters reports that there is also a version that targets Windows PCs.

The malware on the developer computers then attempted to transmit information back to the hackers.

It’s not clear from these reports exactly how much information got leaked, or what kind of information the hackers were seeking. Microsoft says no customer data was compromised. Facebook also said earlier this month that no customer data got out.

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Also unclear: The source of these attacks. However, Reuters reports that the attacks may have originated in China. A widely-publicized report from Mandiant this week identified a People’s Liberation Army unit, called APT1, which it claims has been responsible for a long-term, sophisticated cyber espionage campaign.